This invention relates to a pivotal closing member, and particularly to a throttle valve for the control of the feeding of the fuel-air mixture of an internal-combustion engine. More particularly, the present invention relates to a throttle valve that is fastened to a shaft rotatably mounted in a housing and that is yieldably urged toward a selected end position by means of a pull-back spring system.
It is known to provide a carburator for internal-combustion engines wherein the carburator includes a throttle valve held in a closed end position by means of a tension spring. (Journal Revue Technique Automobile, June 1982, No. 423, Page 12).
One object of the present invention is to provide a return spring system for a throttle valve that is secure and easy to assemble. Another object of the present invention is to provide a return spring system for a throttle valve that is compact and reliable.
According to the present invention, a return spring system includes a first coiled spring, a second coiled spring having a diameter greater than the diameter of the first coiled spring, a hat-shaped bushing for separating the two coiled springs and a lever for simultaneously loading both coiled springs. The spring system is positioned at one end of a throttle valve-carrying shaft and operates to yieldably rotate the shaft in a selected direction to orient the throttle valve.
One feature of the present invention is the provision of two coiled springs also referred to as leg springs. If one leg spring fails or is otherwise inoperative, the other leg spring will operate to bias the throttle valve. Thus, the present invention reliably and advantageously prevents an internal-combustion engine from operating in an uncontrolled manner over an undesirable speed range. Also, both leg springs are compact and require little space. Moreover, assembly of the two leg springs and the bushing separating them is very simple. Use of the lever to prestress or load these leg springs is easily accomplished due to their particular arrangement and interaction with the lever.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purpose of illustration only, an embodiment in accordance with the present invention.